The present invention relates generally to oxygen generators and, more particularly, to a novel molecular sieve oxygen generator which produces oxygen from compressed air without using an external compressor.
Molecular sieve oxygen generation systems (MSOGS) require a source of compressed air in order to produce a supply of oxygen. These devices typically employ a cylindrical adsorbent bed containing a molecular sieve, which is an inert ceramic material designed to adsorb nitrogen more quickly than oxygen. In operation, a stream of compressed air (20-80 psig) is injected into the sieve bed. As pressure builds in the bed, nitrogen molecules attach themselves to the sieve while oxygen molecules pass through as the product gas. Eventually, sieve in the bed becomes saturated with nitrogen molecules and needs to be regenerated. This is done by venting the pressure in the sieve tank to the atmosphere. The nitrogen molecules previously attached to the sieve are released and within a few seconds the sieve bed is ready to begin accepting the feed air supply and producing oxygen again. The oxygen and air flows are controlled automatically by electrically operated solenoid valves. The pressurization/depressurization cycle does not degrade the sieve's adsorption capability. Therefore, the system can be run indefinitely to produce a steady stream of high purity (about 95%) oxygen.
A working system will often employ two such sieve beds and alternate them between pressurization and depressurization. In a typical two-step cycle, during step 1 of the cycle one bed receives high pressure feed air which pressurizes the bed and establishes a product oxygen flow. Simultaneously, the high pressure gas in the other bed is vented to the atmosphere, and this depressurization serves to desorb the nitrogen previously adsorbed during the high pressure phase of the cycle. Also, a portion of the product gas from the high pressure bed may be fed to the low pressure bed to flush the nitrogen-rich gas from that bed. In step 2 of the cycle the adsorbent beds exchange roles. This constant cycling results in a continuous product stream of high purity oxygen.
One conventional method for supplying the sieve beds with the pressurized source air is to use an external compressor. Air is drawn into the compressor, pressurized and then held in a storage tank. The MSOGS then runs off the compressed air from the tank. A limitation of such a system lies in the size and complexity of the various components. The external compressor is; usually large and heavy, and the tank can be bulky as well. These physical constraints can limit the transportability of the unit. Another method of supplying compressed air to MSOGS used on board aircraft is to utilize engine bleed air. This source of air is limited in quantity, can be filled with contaminants from the engines, is not available when the engine is shut down, and can sometimes be difficult to tap into.
It is therefore a principal object of the present invention to provide a molecular sieve oxygen generator which operates without an external compressed air source.
It is a further object of the invention to provide a compact, portable oxygen generator.
It is an advantage of the present invention that it provides a relatively simple apparatus for generating high purity oxygen.
Objects and advantages of the invention are set forth in part herein and in part will be obvious herefrom, or may be attained by means of instrumentalities and combinations pointed out in the appended claims.